Treatments with implantable neurostimulation systems have become increasingly common in recent years. While such systems have shown promise in treating a number of conditions, effectiveness of treatment may vary considerably between patients. A number of factors may lead to the very different outcomes that patients experience, and viability of treatment can be difficult to determine before implantation. For example, stimulation systems often make use of an array of electrodes to treat one or more target nerve structures. The electrodes are often mounted together on a multi-electrode lead, and the lead implanted in tissue of the patient at a position that is intended to result in electrical coupling of the electrode to the target nerve structure, typically with at least a portion of the coupling being provided via intermediate tissues. Other approaches may also be employed, for example, with one or more electrodes attached to the skin overlying the target nerve structures, implanted in cuffs around a target nerve, or the like. Regardless, the physician will typically seek to establish an appropriate treatment protocol by varying the electrical stimulation that is applied to the electrodes.
Current stimulation electrode placement/implantation techniques and known treatment setting techniques suffer from significant disadvantages. The nerve tissue structures of different patients can be quite different, with the locations and branching of nerves that perform specific functions and/or enervate specific organs being challenging to accurately predict or identify. The electrical properties of the tissue structures surrounding a target nerve structure may also be quite different among different patients, and the neural response to stimulation may be markedly dissimilar, with an electrical stimulation pulse pattern, pulse width, frequency, and/or amplitude that is effective to reduce affect a body function one patient potentially imposing significant discomfort or pain on, or have limited effect for, another patient. Even in patients where implantation of a neurostimulation system provides effective treatment, frequent adjustments and changes to the stimulation protocol are often required before a suitable treatment program can be determined, often involving repeated office visits and significant discomfort for the patient before efficacy is achieved. While a number of complex and sophisticated lead structures and stimulation setting protocols have been implemented to seek to overcome these challenges, the variability in lead placement results, the clinician time to establish suitable stimulation signals, and the discomfort (and in cases the significant pain) that is imposed on the patient remain less than ideal. In addition, the lifetime and battery life of such devices is relatively short, such that implanted systems are routinely replaced every few years, which requires additional surgeries, patient discomfort, and significant costs to healthcare systems.
While rechargeable implanted devices have been investigated, the location and depth at which neurostimulation devices are implanted makes recharging of such devices difficult. For example, neurostimulation devices are typically implanted beneath a thin layer of muscle and fatty tissues in a lower back region such that conventional methods may utilize invasive techniques, such as recharging through a transcutaneous cable, or increased device size which may cause discomfort and limited mobility for the patient. Furthermore, given the location at which such devices are implanted—the lower back—attaching a recharging cable or device can be difficult, if not impossible, for a patient to perform without the aid of another person.
In view of these drawbacks associated with conventional systems, the tremendous benefits of these neural stimulation therapies have not yet been fully realized. Therefore, it would be desirable to provide improved methods, systems and devices for facilitating recharging of an implanted neurostimulation device. It would be particularly helpful to provide such systems and methods that recharge an implanted neurostimulation device in a non-invasive manner, while improving ease of use for the patient as well improved patient comfort and mobility during charging.